A federal court ruling issued before the Thanksgiving holiday appears likely to end nearly three years of patent litigation between Histogen, a San Diego regenerative medicine startup, and Carlsbad, CA-based SkinMedica, which provides cosmetics and skin-care products.

“We are happy to now have this matter officially behind us,” Histogen founder and CEO Gail Naughton says in a statement issued today by the San Diego startup.

The Nov. 21 ruling issued by U.S. District Judge Janis Sammartino concludes that Histogen is not infringing on two key SkinMedica patents. “The cloud has lifted for us,” Histogen spokeswoman Eileen Naughton Brandt told me this afternoon.

A spokeswoman for SkinMedica declined to comment today.

In its patent infringement lawsuit, SkinMedica alleged that Histogen and its cosmetics subsidiary, Histogen Aesthetics, were infringing on the patents covering its “NouriCel” product line and related proprietary technology for culturing human cells in growth media.

Histogen is focused on the long-term development of living tissue skin grafts and related products that would require regulatory approval. To generate revenue in the meantime, however, the startup formed Histogen Aesthetics to develop its own brand of skin care and dermatology products. Histogen says it also has begun early tests of a hair replacement product made of growth factors and other compounds expressed by fibroblasts, the cells that form connective tissue.

In her 14-page ruling, Sammartino distinguishes between SkinMedica’s patented process for growing a three-dimensional matrix of living human cells and Histogen’s approach, which encourages living cells to grow on the surface of microscopic beads. The cell-covered beads eventually clump together, and also grow into a three-dimensional matrix. By drawing a clear distinction between the two processes, Sammartino rejects SkinMedica’s arguments that the two approaches were equivalent.